(Just Copy and paste the above Command in RUN)You should be able to launch Tweak UI, as well as the Registry Editor.

Method 2: Using the Group Policy Editor (Windows XP Professional only)

Click Start, Run and type gpedit.msc and press ENTER Go to the following location:

User Configuration Administrative Templates System

Double-click Disable registry editing tools and set it to Not Configured

Exit the Group Policy Editor Note: If the setting already reads Not Configured, set it to Enabled, and click Apply. Then revert it back to Not Configured. This ensures that the DisableRegistryTools registry value is removed successfullyso enjoy this trick